Driveline vibration

[76m2002]

I've got a weird driveline vibration in our '91 318is.  I can feel it in the seat, not the steering wheel, so I don't think it's steering-related.  It occurs at all speed and rpm, and gets more noticeable at higher speed/rpm.  I've installed new motor mounts, transmission mounts, guibo and center bearing.  I did also recently install a new clutch and flywheel, as well as an oem rear muffler section.

I'm flumoxed.  Suggestions?  Can the oem driveshaft become unbalanced??

[DesktopDave]

Did you match the two halves back up after you did the CSB?  They should have two paint marks to preserve the factory balancing job.  The CSB itself should also be pre-loaded as well, toward the front of the car 2-3mm.

I've seen balancing weights spot-welded to the driveshaft sections, I suppose it's possible that they've gone away.  Or the rear u-joint is on the way out.

Have you determined that the diff & rear half-shafts are in good shape?  What about the diff ear mount and the subframe mounts?

[fumstoo]

^^ Id be willing to bet anything its something to do with your driveshaft being off balanced. When i swapped to g260 i thought about shortening it myself but anything driveshaft related should be left to the pros, in my opinion.